biology-blueprint-of-life.pdf

7/26/2019 Biology-Blueprint-of-life.pdf

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Biology - Blueprint of life

1. Evidence of evolution suggests that the mechanism of

inheritance, accompanied by selection, allow change over

many generation

Outline the impact on the evolution of plants and animals of: Changes in physical

conditions in the environment, Changes in chemical conditions in the environment and

Competition for resources

Evolution: the change in a species over time

Change in environment is the driving force behind evolution. Environmental change limits

resources, placing selective pressures on organisms. Competition for resources will arise.

Survival of the fittest occurs- those with favourable characteristics survive and reproduce.

Changes in physical environment (temp, water & light availability, wind):

Changes in Aus phsical environment in the past !" million ears, has led to evolution: #ncreased aridit led to decrease in rainforests and increase in grasslands and

woodlands.

$ring up of la%es led to species that could conserve water e.g. water-holding frog

Changes in chemical environment (gas and salt levels, pH):

&he increasing o'gen levels in the environment when photosnthetic organisms

appeared on Earth, led to aerobic (respiring) organisms.

$$& resistant mos*uitoes

Competition for resources (food, water, nesting sites, mates):

Competition can occur within or between species #n Aus, the introduced species (rabbits, cane toads) has caused competition with

native species, leading to the e'tinction of man species. E.g. the European rabbit

has outcompeted the bilb and +itou bush has outcompeted Acacia in man areas

Analyse information from secondary sources to prepare a case study to show how an

environmental change can lead to changes in a species

Species:mos*uitoes

Environment change: spraing of insecticides such as $$& to %ill mos*uito cause a chemical

change in the environment

Change within species: increase in fre*uenc of pesticide resistance in the species.

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esult: 2ost of the mos*uito population, who were not resistant to $$&s, died out. &hose

few individuals resistant to $$&s due to random mutation, survive and pass on favourable

characterises to offspring. &his resulted in an increase in fre*uenc of pesticide resistance in

the species3 evolution

Describe, using specific examples, how the theory of evolution is supported by the

following areas of study, (1 !alaeontology" including fossils that have been considered to

be transitional forms, (#$iogeography, (% Comparative embryology, (& Comparativeanatomy, ('$iochemistry

. !alaeontology " (study of fossils)

#ossils:an preserved remains or traces of past life preserved in roc%, ice, amber, tar, volcanic

ash.

1ossils show the evolution of organisms that originated from a common ancestor, revealed in

transitional fossils. &hese are the missing lin%s between groups - e'hibit characteristics of

two different groups of organisms and reveal a successive change in a species over time

Evidence:Archaeopter' shows a transition between reptile to bird. #t has the long-bon tail,claws and reptilian teeth of a reptile, but a wish-bone, feathers and wings of a bird.

Seed ferns show a transition between ferns (reproduce b spores) and conifers and flowering

plants (reproduce b seed-bearing).

$imitations: 1ossil record is incomplete, bias towards organisms with bod parts better suited

to fossilising (4ac% of soft-bodied5earl organism fossils)

!. %iogeography (study of geographical distribution of organisms)

A new species arises when a group of organisms become isolated from the rest of the

species and are faced with different environmental pressures, supporting evolution from acommon ancestor.

Evidence: 1lightless birds - emus in Aus, %iwis in 67, ostriches in South Africa, and rheas in

South America. &hissuggests these birds originated from a common ancestor on 8ondwana,

and evolved on the isolated continents

4imitations: 4imited to studies of species which have become isolated at some point

9. Comparative embryology (comparing development stages of embryos of different

species)

Similarities in embronic development suggest a common ancestor.

Evidence:the embros of different vertebrates are ver similar in earl stages. E.g. fish,

amphibian, reptile, bird and mammal embros all show gill slits and tails at some stage

0. Comparative anatomy (study of similarities and difference in structure of organisms)

Similar structures are evidence that the evolved from a common ancestor

Evidence:omologous structures are evidence for divergent evolution. &hese are organs that

have the same basic structure, but with different functions, that have derived from a

common ancestor. E.g. ;entadactl limb possessed b all vertebrates (wing of bird, forarm ofli


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Some homologous structures have become vestigial structures, remnants of bod parts no

longer useful e.g. human appendi'

Analogous structures are evidence for convergent evolution. &his is the evolution of

structures to serve a common purpose in a common environment, but do 6>& share a

common ancestor. E.g. protective spines of Aus echidna and Euro hedgehog to discourage

predation

$imitations: 1ossils are incomplete and bias, confusion between analogous and homologous

". %iochemistry (study of chemicals in cells)

>rganisms that share a common ancestr also share the same basic biochemistr. E.g.

humans and chimpan


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6ew technologies (e.g. $6A hbridisation, amino acid se*uencing) have allowed comparison

of chemicals in organisms, increasing %nowledge about the relationships between species.

&hese have produced evidence to both support and disprove traditional classification

schemes

Change in evolutionary thin-ing:

&hese technologies have improved our understanding of humans relationship to

chimpan


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other parents traits E.g. tall:short 3 9:, %nown as the monohbrid ratio. e states that this

other factor (short) was recessive and mas%ed b the dominant factor.

e developed mathematical ratios, summed up in .endel/s law of dominance and

segregation

Characteristics are not blended, but are discrete units

Each characteristic is determined b a pair of factors (genes)

#n a gametes, onl one factor is present $uring fertilisation, the offspring receives one factor from each parent randoml

>ne factor is dominant of the other, which is recessive the $>6& blend

Describe the aspects of the experimental techni/ues used by .endel that led to his success

0alid and reliable:

Studied onl one characteristic at a time:changed onl one variable and controlled

all others

;erformed a large number of crosses - reliabilit

'ccuracy:

&ightl controlled fertilisation: /emoved immature of stamen to stop the prevent self-pollination

8rew plants in separate green-house to prevent accidental cross-pollination

2anuall transferred pollen from one pure-bred plant to the stigma of the other

used a plant with easil identifiable characteristics

Describe outcomes of monohybrid crosses involving simple dominance using .endels

explanations

when two pure-breeding parents with contrasting alleles are crossed, the create

monohbrids

E.g. a homozygous (TT) tall plant crossed with a homozygous (tt) short plant 1 3 all hetero


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1or ever characteristic, there are two alleles in the genotpe.

#n a hetero


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Egg and sperm each contribute half of the chromosomes to the


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Describe the inheritance of sex5lined genes, and alleles that exhibit co5dominance and

explain why these do not produce simple .endelian results

Co"*ominance: ?hen neither allele is dominant over the other, resulting in both being

e'pressed in the phenotpe. E.g. roan-coloured cattle

#f Shorthorn cattle has the gene for red and

white hairs, both will be e'pressed3 roan

$oes not give the simple 2endelian ratio of 9:,because a hetero


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Outline the ways in which the environment may affect the expression of a gene

&he environment ma hinder or enhance the e'pression of a gene.

Hydrangeas: the acidit or al%alinit of soil influences flower colour. Acidic soil 3 blue,

al%aline 3 pin%

Human growth: human height has a genetic basis, but a lac% of nutrients or presence of

to'ins (cigarette smo%e) can restrict growth

Construct a model that demonstrates meiosis and the

processes of crossing over, segregation of chromosomes

and the production of haploid gametes

$. %he structure of &'( can be

changed and such changes may be

reflected in the phenotype of the affected organism!

Describe the process of D4A replication, and explain its significance

*+' replication"the process b which an e'act cop of $6A is made, during mitosis and

meiosis

!rocess:

Catalsed b the en


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Simple model:

)xplain the relationship between polypeptides and proteins

A protein is a comple' molecule made up of one or more polpeptide chains, folded into a

particular shape, to suit a specific function.

A polpeptide is made up of amino acids lin%ed b peptide bonds.

Discuss evidence for the mutagenic nature of radiation

#n the earl Ds, the harmful effects of radiation were un%nown and scientists, such

as 2aria Curie, were e'posed to large amounts of radiation over long periods of time.

Curie died from 4eu%aemia due to overe'posure to radiation

F= radiation has been recorded to increase the incidence of s%in cancers in humans.

Survivors of iroshima bombing and the nuclear meltdown at Chernobl suffered

mutations such as infertilit and cancers, as a result of being e'posed to high-levels of

radiation

)xplain how mutations in D4A can lead to the generation of new alleles

2utations are an changes in $6A se*uence. &his results in changes to the amino acids that

are produced, meaning there is a source of new alleles. &o produce changes in alleles, the

mutation must occur in the se' cells of the organism which are then passed on to the ne't

generation. &hese changes to the genes result in the production of new proteins. 2ost

mutations are not harmful and lead to variation, but some will lead to genetic disorders.

)xplain a modern example of 8natural selection

"he $eppered %oth#

>riginall population was mainl composed of lighter moths

&he camouflaged on lichen covered trees to hide from birds

$uring #ndustrial /evolution, trees covered in soot and lichen die off

4ight moths can no longer camouflage, become easier pre. $ar%er moths can hide

better now

;opulation shifts from mainl light to mainl dar%.

)xplain how an understanding of the source of variation in organisms has provided

support for Darwins theory of evolution by natural selection

$arwins theor re*uires variation to be present within an organism. ?e now %now the

source of this variation:

2utation of the base se*uence of $6A

&he random segregation of chromosome pairs during meiosis

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Crossing over of genetic material during meiosis

/andom fertilisation of se' cells

&hese support his theor as the provide the mechanisms for variation on which natural

selection act.

Describe the concept of punctuated e/uilibrium in evolution and how it differs from the

gradual process proposed by Darwin

*arwin/s 1radualism:

e proposed that populations change graduall over a long period of time

e used transitional fossils to support this

!unctuated Euilibrium:

;ut forward b 8ould and Eldridge

&hat evolution occurs in short bursts of rapid change, followed b long periods of

stabilit

&he fossil record shows millions of ears passing without an notable change, and

then evolve suddenl (e.g. soft-bodied organisms dominated the seas for hundreds

of millions of ears, and then, in the space of a few million ears, the disappeared)

Analyse information to outline evidence that lead to $eadle and 7atums 8one gene 6 one

protein hypothesis and explain why this was changed to 8one gene 6 one polypeptide

%eadle and 2atum

&he sub@ected the spores of bread mould to I-ras in order to cause mutations and

found that some of the mutated spores could not grow on the nutrient base of bread

unless the added a specific amino acid arginine

&he hpothesised that the I-ras had destroed the gene that coded for the protein

arginine calling this the one gene one protein hpothesis

&his was later changed to one gene one polpeptide, because man proteins are made up

of more than one polpeptide, and a gene onl codes for one polpeptide.

!rocess information from secondary sources to describe and analyse the relative

importance of the wor of 9ames +atson, rancis Cric, ;osalind ranlin and .aurice

+ilins in determining the structure of D4A and the impact of the /uality of collaboration

and communication on their scientific research

1ran%lin was a woman wor%ing in a predominantl male field. +efore publishing her wor%,

she wished to gather more evidence but ?il%ins showed her results to ?atson and Cric%

without her permission. &his information was enough for ?atson and Cric% to develop their

model of the double heli' structure of $6A.

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&cientist 'ole

1ran%lin Fsed I-ra crstallograph to discover that the shape of the $6A molecule was

a heli'

?il%ins Studied the structure of large molecules. #nformed ?atson and Cric% of

1ran%lins discoveries

?atson ?or%ed with Cric% to model the structure of the $6A molecule. Suggested that

pairing of bases made it possible to cop and pass on genetic information

Cric% ?or%ed with ?atson to model the structure of the $6A molecule. Studied the

genetic code.
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?atson and Cric% wor%ed well together. &he published their findings with each other.

1ran%lin died of cancer in "D. 0 ears later the other three were awarded the 6obel ;ri


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easons:creating foods with increased nutrients and higher ields. #ntroducing resistance in

species to disease, pests and pesticides

!rocess:cut, cop and paste

. cut- a gene for a favourable characteristic is removed from the cell of an organism,

using restriction en


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Environmental

issues

/educes use of pesticides 4oss of biodiversit

;otential for escape of the

transgenes into other

populations

Speeds up genetic change in a

species

#inancial &

social 5ustice

issues

#ncreases production of food for growing

human population igher ield at lower cost

4ess spoilage of produce during

transportation

#s it ethical for single

companies to have the rightsto these technologies while

others dont, creating a

monopol

Health issues 1oods with higher nutritional value can be

developed

/educes use of pesticides

;lants can produce vaccines to improve

human health

Safet of 82 foods un%nown

especiall for people with

allergies

Human rights

issues

82 crops ma be used to solve food

shortages in third-world countries,

producing a higher ield at lower cost

=egetarians ma un%nowingl

eat food with animal genes

#f a human gene is inserted

into an animal, are we

humanising itL #s it acceptable

to eat the meat of an animal

that contains human genesL

Discuss the potential impact of the use of reproductive technologies on genetic diversity of

species using a named plant and animal example that have been genetically altered

/eproductive technologies often lead to a decrease in biodiversit, as large numbers of

identical organisms are produced and bred (e.g. through cloning) or if organisms are

selectivel in-bred to maintain parent lines of hbrids that benefit us in terms of agriculture

produce. A lac% of variation is a ma@or ris% factor in e'tinction of a species, as the are less

li%el to survive sudden environmental change or would be vulnerable to pathogens.

1enetically modified plants:

E.g. +t cotton is rapidl replacing other varieties of cotton in commercial agriculture.

$isadvantages:

2an natural varieties of cotton will be lost

aving a monoculture means that the crop becomes more susceptible to

environmental change and ma also lead to +t resistance in insects

1enetically modified animals:Some salmon have been geneticall modified so that the grow bigger than normal salmon.

1emale salmon are attracted to and mate more often with larger males. #f the transgenic

salmon were to be released in the wild population then wild females would mate with the

larger transgenic males. &his transgene would rapidl spread in the natural population,

reducing diversit.

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